src/sim/cell/materials/gas.rs


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use rand::RngExt;

use crate::sim::cell_sim::sim::{PostUpdateAction, UpdateCtx};

#[inline]
pub fn sim_update(ctx: &mut UpdateCtx) -> PostUpdateAction {
    // only allow upward movement some of the time to limit movement speed
    if ctx.rng.random_range(0.0..1.0) > 0.8
        && ctx.swap_or_settle(&[(0, -1)]) == PostUpdateAction::None
    {
        return PostUpdateAction::None;
    }
    // same for each horizontal direction
    if ctx.rng.random_range(0.0..1.0) > 0.8
        && ctx.swap_or_settle(&[(1 - ctx.seqno_parity as i32 * 2, 0)]) == PostUpdateAction::None
    {
        return PostUpdateAction::None;
    }
    if ctx.rng.random_range(0.0..1.0) > 0.8 {
        return ctx.swap_or_settle(&[(-1 + ctx.seqno_parity as i32 * 2, 0)]);
    }

    PostUpdateAction::Apply
}